The ‘industry standard’ of 1000 IMC, 500 VMC originated from the FSF CFIT and ALAR safety initiative. This was a ‘committee’ decision involving manufactures, operators, unions, and ATC; the heights were readily accepted, but not so the speed limits. There was a general view that Vref+15 should be used, but because Boeing had already published Vref+20, the money won.
There is continuing debate about the value of ‘fixed’ limits, particularly where ‘inappropriate values’ (crew perception) might result in crews deviating from the norm -
Go-Around Safety Forum.
The safety objective of a stable approach is to reduce the probability of an overrun. In this, speed deviation appears to be the most critical factor (with tailwind and wet runway). Speed is the ^2 term in energy, thus the crew’s primary aim is to manage the aircraft’s energy. The objective is to cross the threshold at Vref (or at approach speed providing the required landing distance is adjusted) and to avoid a long landing.
Even with criteria of Vref +20 at 500ft, the approach will not be ‘stable’ as the aircraft is required to decelerate to Vref at the threshold – can your aircraft can decelerate by 15-20kts during the remaining descent.
Thus depending on aircraft type it might be more beneficial to work back from the threshold requirements, considering a realistic deceleration - without using idle power / airbrake, and accounting for tailwind and eng anti-icing use, to determine the alt/speed gate which would define a stable approach.
IMHO the threshold values are best met before 100ft, and the deceleration (energy reduction) flown according to conditions – crew decision.
Thus a good approach briefing is essential to define the point of stability. In some cases the landing distance available (safety margin) might indicate the need of a much earlier stable approach due to the necessity of accurate touchdown position and airspeed.
The HF argument is that crew’s are more likely to adhere to a limit which they chose than some fixed value, particularly when judged not necessary for the condition. The hazard is that the crew might not select a value suitable for the conditions, but even so is this hazard any greater risk than violating a rule.